Perinatal pathology is not a common topic in the general pathology literature and is often considered a subspecialty restricted to pediatric pathologists. Nevertheless, many general pathologists in community practice are periodically faced with challenging cases in perinatal pathology, be it in the form of perinatal postmortem, placental, or surgical pathology specimens. Perinatal complications, such as premature birth, stillbirth, and congenital disease, are indeed common occurrences in every part of the world and by no means restricted to centers with subspecialty trained pathologists. Such cases may be overwhelming when one has little familiarity with this type of specimen. The expectations of the clinician (neonatologist, obstetrician, or geneticist) and, even more importantly, of parents looking for answers may even be perceived as intimidating. One of the challenging components of perinatal pathology is the placental examination whose importance as an adjunct to the neonatal autopsy cannot be overemphasized. A previous issue of this journal provided an excellent selection of topics covering the placenta (see Dr Lange's "New entities in placental pathology for the practicing pathologist," Pathol Case Rev. 2010;15:35-36). The current issue, which focuses on the fetal/neonatal specimen, will complete the circle by providing some practical guidelines through the illustration of typical case scenarios encountered in the perinatal age group.
It would be impossible to address all areas of perinatal pathology in this format as it encompasses so many organ systems. The following selection of articles will attempt to review a wide variety of topics, from early fetal developmental disorders, infection, cardiac malformation, perinatal brain injury to molecular pathology.
The first article, "Fetal hydrops: A systematic approach for the pathologist," by Dr Hartman and myself provides a review of immune and nonimmune fetal hydrops following the description of an interesting case example where several factors/mechanisms contributed to the development of hydrops. The pathophysiology and etiology of the different forms of hydrops are reviewed, and a systematic approach in the workup is offered.
The next 2 articles, both kindly provided by Dr Pinar, exemplify the breadth of perinatal pathology: the first, titled "Hydranencephaly," illustrates the point that an enlarged head diagnosed prenatally or at birth does not equate hydrocephaly in every case. He describes the unique features of hydranencephaly and elucidates its mechanism of development. His second article, "Listeriosis," emphasizes the placental pathology encountered in Listeria infection and its differential diagnosis. The microbiological uniqueness of this organism with its epidemiological and clinical consequences is described.
Another beautiful demonstration of the interplay between placental and fetal development is provided by Sarah Shulman and Dr Shehata with their article, "Amniotic band syndrome: Characteristic manifestations of ABS in three cases." Here the authors illustrate the spectrum of this interesting disruption sequence and review the different pathogenetic theories, differential diagnosis, and treatment modalities.
With Dr Kearney's article, "Ductus dependent congenital heart disease in the neonate," we now enter the particularly challenging area of cardiac perinatal pathology. Dr Kearney leads us step by step through the process of how to correctly examine the perinatal heart at autopsy and how to distinguish the different types of ductal-dependent lesions. The pathophysiology and clinical significance of these congenital malformations are reviewed as well.
We then move to another challenging field, perinatal neuropathology. Dr Folkerth, in her article, "Principles of perinatal hypoxic-ischemic brain injury: Four illustrative cases," gives us different case examples, each illustrating an important category of hypoxic brain injury. She describes a stillborn with diffuse white matter gliosis, a preterm infant with periventricular leukomalacia, a preterm infant with germinal matrix hemorrhage and a term infant with congenital heart disease and hypoxic-ischemic encephalopathy. The respective clinical, gross, and microscopic findings are reviewed.
Finally, Drs Velagaleti and Moore, with their article, "The role of array comparative genomic hybridization in investigation of cytogenetic causes of pregnancy loss," close this issue with a discussion of the important subject of perinatal molecular pathology. Currently, conventional karyotyping and/or fluorescence in situ hybridization are the most commonly used methods to determine a chromosomal abnormality in products of conception. These techniques are fraught with limitations such as growth failure and contamination. Failure to achieve results can be distressing to parents who seek an explanation for pregnancy loss. The advantages and the potential future role of comparative genomic hybridization technology are described.
I am grateful to all the authors who have contributed to this issue. I hope that it will prove to be useful to the practicing pathologist who faces the challenge of a perinatal specimen.